Method of packaging electric blasting caps



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H. B. ALEXANDER ETAL METHOD OF PACKAGING ELECTRIC BLASTING CAPS Filed Feb. 8, 1940 EEEEE EEEEE NNNNN HAM/7 B. ALEXANDER,

Cam/5L4 H. CORD/E.

INVENTORS NNNNN EEEEE EEPEE NNNNN NNNNN EEEEE EEEE July 4, 1944.

Patented July 4, 1944 BLASTlNG C APS Harvey B. Alexander, Kenvil, N. J and Cornell Gordie, Wilmington, Del., assignors to Hercules Powder Company, Wilmington, Del., a corporation of Delaware Application February 8, 1940, Serial No. 317,988

3 Claims.

This invention relates to special receptacles and a method of packaging, and more particularly to the packaging of electric blasting caps.

Electric blasting caps usually comprise a shell for the detonating material and leg wires extending from the shell adapted to be connected to a source of electrical energy. To facilitate packing and handling electric blasting caps, the leg wires are usually folded into loops which may be bundled about the shell and may be held in place by a paper wrapper or a cardboard tube; The caps assembled in this manner are then packed in boxes or cartons adapted to contain 25; or 50 or any desired number of blasting caps; Since the detonating material employed is of a highly sensitive nature, numerous precautions must be taken to prevent premature explosions or firing of the caps. Such precautions must be taken, particularly when the caps are packaged in lots of 25 01"50 and apremature-explosion of one cap mayset off all or a great number of caps in-a carton. A recommended precaution and Government specification for minimizing this contingency is that a carton of caps as usually packed and shipped by the manufacturer shall be able to pass'what is known as a container propagation test. j lhis test comprises taking the leg 'wires of a blasting cap or detonator located approximately in the middle of a'ca'rton ofidetbhatorsand connectingthe wires to a source of electriccurrent; The 'cart'on is placed in an enclosure, such as a 50 gallon steel'd'ruin with the 'open end partially' covered, and the cap 'selectedis then fired. bsi fier th nu ber "o n iQh r hot fired by the blast are counted and the percentage ofcaps which were fired is calculated. To pass this testless than 25% of the caps in the carton mayb 'fi d. V I All objectjof the present invention is to pack- .age'fblasting caps, 50 that they will readily pass the foregoing described propagation test. v, Q Anotherobjectis to provide an improved blasting cap] package. r

I Another object is to provide an improvedmethodv of packing blasting capsin cartons and the like."',-. l

'A'Lfurthe'r obj'e'ct'is to arrange blasting caps in cartons in such a manner that a minimum number of caps are fired during the propagation test. l'Qther and further objects willbe obvious upon an understanding of the illustrative embodiment about toibe described, orwill be'indicated 'inl the appended claims, andivarious. advantages not referred to herein will occur tojon'e skilled in the art upon employment'of'the invention in practice.

These objects, in general, may be accomplished by folding the leg wires into loops and bundling the loops. The end of the blasting cap shell where the detonating charge is located is positioned adjacent one end of the bundle of loops and the cap and leg wires'are placed intoa card board tube. This tube preferablyhas indi'cia at the end where the cap is locatedi 'Iihese' units are then packed in cartons by placing "them in: groups of substantially horizontal and vertical. rows with no more than two tubes having theidet: onating. charge at the same end disposed side-by side in at least one of jthegroups of rows.

An embodiment of the invention has beencjhos en .for purposes of, illustration and description and is shown in the accompanying drawing, forming a part of the specification, wherein j V Fig. 1 is a side view, partly sectional, illustrating a blasting cap unit in accordance with the present invention; i

Fig. 2 is a top plan view of an open carton illustrating anumber of blasting cap units packed therein;

Fig. 3 is adiag'rammatic front .elevational view illustrating the arrangement of a number.ofblastT ing capunits in a carton;

. Fig. .4 is-a diagrammatic front el'evational view illustrating another arrangement of .the blasting capunits; I

Fig. ,5 is a diagrammatic front elevationalview illustrating still another arrangement. of the blastingcapunits;and" Q Fig. 6 is a diagrammatic frontelevational view illustrating a modified. way of packing, the. blasting cap units when arrangedas shown'in either Fig. 3,.Fig. l. or Fig. 5. I L

Referring to the drawing, and' moreparticularly to Fig. '1, there is shown by w'ayof example, an electric blasting cap shell in having a detonating charge adjacent its closed end ill and fitted with an electricalfiring device (not shown) which may be electrically connected by leg wires lzlextending from the other end 14 of the shell. lhe shell is about of an inchin diameter and between about 1 /2 to 2 inches in length and the leg wires are between about 4 to 20 feet in length, although longer wires maybe provided if 'lde sired.

. These leg wires are preferably folded'intorelatively short loops of about between} to l flins. in'length and the loops are bundled'together." l n order to provide for safer packing of a group of electric blasting caps, as will be described'here inafter, and to meet propagation requirements, the end H of the shell containing the detoiiatingcharge is located adjacent one end of the bundle of loops.

The shell and leg wires assembled in this manner are inserted into a cardboard tube 15, the wall 16 of which has a thickness of between about .030 and .035 of an inch. The tube preferably is cylindrical and has an inside diameter of about A of an inch and may be between about 3 and inches in length depending upon the length of the leg wire. For example, a tube 3 inches in length usually is suitable for accommodating a cap with folded leg wires of 4 to 6 feet, while a 10-inch tube may be used for those with leg wires of about feet. Also, if desired, the tube length may be 3 inches in length for leg wires of varying lengths and the diameter of the tube may range, for example, from of an inch to 1 inch to accommodate the wires.

As noted in Fig. 1, the cardboard tube is approximately twice as long as the shell and by placing the shell .so that the end containing the charge is adjacent one end of the tube, the explosive charge is substantially removed from the other end of the tube. Thus one end of the tube may be termed the explosive end E and the other end the non-explosive end N.

In order to enable blasting operators to determine at a glance, at which end of the tube the shell is located, one end of the tube is provided with suitable printed indicia. l9 or the like. This indicia preferably is provided on the exterior of the tube and, for example, may comprise an annular zone of ,circumferentially spacedlongitudinally extending bars or any other suitable marking. When the caps and leg wires are inserted into the tubes, the explosive end of the cap shell is placed at or adjacent the end of the tube bearing the indicia. Thus when the caps are to be used, the blasting operators can tell immediately where the cap is located and can remove it from the tube more quickly and with greater safety. Also, by providing the indicia 19, the about to be described method of packing the units in cartons can be carried out conveniently.

In Figs. 2 and 3, a preferred method of arranging the assembled blasting cap and tube units is illustrated. Fifty units, for example, are packed in a cardboard container, 20, having the usual bottom, side walls, and a folding top or cover. The tubes l5 containing the blasting caps are arranged in groups of substantially horizontal and Vertical rows. The explosive end E of alternate vertical rows of units faces in one, direction, that is, each alternate vertical row consists of units having the explosive end E facing in the same direction with the intermediate vertical rows having the explosive end facing in the op posite direction. Thus when, for example, the propagating cap P, approximately in the middle of the carton is fired, only the caps above and below it, which have the explosive at the same end should be seriously affected. Since the explosive end E of a minimum number of caps is adjacent the explosive end of the cap fired, a minimum number of caps should be set 01f during the test.

Table I Tube length inches 3 Internal diameter do Thickness of wall do .0- 2 Leg wire length feet 4 Number of units in carton 50 No. of caps Test No. failing to z gg g gg fire Average 45.1 4.9 9. 8

Table II Tube length inches 3 Internal diameter (lo 4 Thickness of wall do .032 Leg wire length feet 6 Number of units in carton N o. of caps 1 Test No. faillng to a ga g gg fire Average 46. 5 3. 5 7. 0

The results of these tests indicate that by employing the method of packing the blasting caps in tubes andpackaging the units so assembled in accordance with the invention, a very small percentage of capswill be fired. In no instance did this percentage exceed 16%, which is well within the permissible 25%. v

Table II illustrates that caps having longer leg wires are afforded even greater protection and thus fewer caps will be fired. In two instances (tests 4 and 6) no caps, other than the caps willfully fired, were fired.

In Fig. 4, a slightly different arrangement of the cap and .tube assembly units is illustrated. Each alternate pair of vertical rows has the explosive end E of theunit facing in the same direction, while the intermediate pairs of rows have the explosiveendfacing in the other direction. 7 r

In Fig. 5 a still different arrangement is illustrated. Alternate units in both the horizontal and vertical rows have the explosive end E facing in the same direction. This arrangement may require a tube having a slightly greater thickness.

In Fig. 6 a modified way of packing the units is shown wherein a cardboard or plywood sheet 22 or the like is placed between adjacent horizontal rows. Such sheets may be used when the cap and tube units are arranged as shown in Fig. 3, Fig. 4, or Fig. 5, and serve to further reduce the number of caps fired.

From the foregoing description, it will be seen that the present invention provides an improved electric blasting cap and tube assembly and an improved method of packing the assembly in cartons. The cartons can be handled more safe- 1y because the caps are protected against shocks which might fire them accidentally. The cartons packed in accordance with the invention are fully within the propagation specifications. The indicia on the tubes enables the units to be arranged in cartons as herein described, quickly and conveniently. All these advantages are attained in a simple and inexpensive manner.

As various changes may be made in the form, construction, and arrangement of the parts herein without departing from the spirit and scope of the invention and without sacrificing any of its advantages, it is to be understood that all matter herein is to be interpreted as illustrative and not in a limiting sense.

What we claim and desire to protect by Letters Patent is: a

l. A package of electric blasting caps comprising a container, and at least about 2'5 circular tubes of a. common diameter, each containing an electric blasting cap shell having a detonating charge therein at one end and adjacent one end of the tube thereby providing a tube with a charged and an uncharged end, said tubes being positioned in said container so that each tube is parallel to the other and lies in a common direction normal to spaced planes parallel to each other and including said tube ends, said tube ends forming rows normal to each other, the tubes in at least one row and not more than two consecutive rows of a common direction having their charged end in a common plane, the tubes in the rows normal to the said common direction rows being arranged so that at least single charged ends and not more than pairs of charged ends are alternately positioned.

2. A package of electric blasting caps comprising a container, and at least about circular tubes of a common diameter, each containing an electric blasting cap shell having a detonating charge therein at one end and adjacent one end of the tube thereby providing a tube with a charged and an uncharged end, said tubes being positioned in said container so that each tube is parallel to the other and lies in a common direction normal to spaced planes parallel to each other and including said tube ends, said tube ends forming rows normal to each other, the tubes in alternate rows of a common direction having their charged end in a common plane, the tubes in the rows normal to the said common direction rows being arranged so that their charged ends are alternately positioned.

3. A package of electric blasting caps comprising a container, and at least about 25 circular tubes of a common diameter, each containing an electric blasting cap shell having a detonating charge therein at one end and adjacent one end of the tube thereby providing a tube with a charged and an uncharged end, said tubes being positioned in said container so that each tube is parallel to the other and lies in a common direction normal to spaced planes parallel to each other and including said tube ends, said tube ends forming rows normal to each other, the tubes in two consecutive rows of a common direction having their charged end in a common plane, the tubes in the rows normal to the said common direction rows being arranged so that pairs of charged ends are alternately positioned.

HARVEY B. ALEXANDER. CORNELL H. CORDIE. 

